The invention relates to a method for trackwise burst error correction, in multitrack storage, based on an error protective code format that comprises first and second linear block codes. Each block code is based on a plurality of symbols, and each individual symbol forms a pivot symbol of a word pair. The word pair consists of one word from either code that have the pivot symbol in common, and have mutually different cross-track orientations.
Error correcting schemes based on so-called Diamond codes, that with respect to the present invention have a somewhat restricted scope, were disclosed in U.S. application Ser. No. 08/304,000 (PHN14909), now abandoned, and U.S. application Ser. No. 08/535,155 (PHN15107), all to the assignee of the present application. Likewise, single- and multitrack error correction schemes based on exclusively convolutional codes have been described in U.S. Pat. Nos. 4,395,768 and 4,486,882 (PHQ81009), respectively, to the present assignee. The previus citations are all hereby incorporated in whole by reference. A diamond code format can be expressed in that first words are disposed across a plurality of tracks running along a tape, whereas second words are disposed across the same plurality of tracks, but at another cross-tape orientation. In this format, user symbols as well as parity symbols are protected by the redundancy of one word from either code. The codes are cyclic or semi-cyclic codes based on multi-bit symbols, in particular (shortened)-Reed-Solomon codes. An advantage of the Diamond format is that the overall code is a finite impulse response code that can be completely self-contained within a finite physical block, yet without adhering to the strict requirements for a block code. The scope of the present invention can be broadened in relation to the Diamond codes, in that other linear block codes can be used for the two separate codes. The multi-bit-symbol restriction as well as the final impulse response are not prerequisites. For brevity, the term Diamond code will be used sometimes hereinafter.
Now, the diamond format encoding does not explicitly address a fault model based on trackwise burst errors; when the format is used in a storage tape organization, whether in magnetic, optical, or other, such trackwise burst could be caused by scratches associated to the tape that moves along the pick-up head and various other media mechanical guidance elements. Another potential fault cause is the breakdown of one or more heads, either at the writing or at the reading operation. There is a need for a strategy that would provide an improved protection, given the existing code format.